The present invention relates to a press for purvulent materials, and particularly to a press for compacting convex or concave articles from metal powder.
As it is well known to the experts of this art all presses for powder compaction existing to-day and the relative dies do not allow for a control and adjustment of the movement of the die elements and the relative reactions to such a movement of same elements during the displacement from one position to another; thereby, it follows that not all the details realizable in theory in their shape with the powder metallurgy technique, with a press of fixed capacity, can in practice be produced and without defects on such a press, insomuch as they require the use of a press endowed with a much greater capacity or even to have recourse to the expedient of producing a rough-shaped piece wherefrom through subsequent mechanical workings the final shape of the detail can be attained.
For example, for compacting an article having a shape different (f.e. concave) from that previously compacted (f.e. convex), it is necessary, in the known presses to radically modify the assemblage type of the press or to change the press itself.
A typical known press arrangement is shown in FIGS. 1 and 2A, 2B and 2C of the drawings. Such a press consists of a hollow die, at least one lower punch P, at least one core A and at least one upper punch S, as shown in FIG. 1. The lower punches P and the core A define the cavity to be filled with a pulverulent material as shown in FIG. 2A, whereas the upper punches S cooperate with the lower ones for compacting the powder and obtaining the finished article.
Generally a semifinished product is firstly produced in a known press as shown in FIG. 3B and then finished by a mechanical removal of the parts T as shown in FIG. 3C.
Likely, when it is necessary to pass from the production of a convex piece as shown in FIG. 4A to the production of a concave piece according to FIG. 4B, the die and punch arrangement must be radically modified or press type must be changed.
Moreover, the presses known up to-day do not provide means apt to control and adjust both the movement of the punches and cores and respective reaction to said movement during the displacement from one to another position thereof. Therefore, as already said, articles having some particular shapes can not be manufactured with the known presses, without the necessity to finish the rough product by a mechanical working.